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SUMMARYThe preparation, initiation and occurrence dynamics of earthquakes in Italy are governed by several frequently unknown physical mechanisms and parameters. Understanding these mechanisms is crucial for developing new techniques and approaches for earthquake monitoring and hazard assessments. Here, we develop a first-order numerical model simulating quasi-static crustal interseismic loading, coseismic brittle episodic dislocation and post-seismic relaxation for extensional and compressional earthquakes in Italy based on a common framework of lithostatic and tectonic forces. Our model includes an upper crust, where the fault is locked, and a deep crust, where the fault experiences steady shear.The results indicate that during the interseismic phase, the contrasting behaviour between the upper locked fault segment and lower creeping fault segment generates a stretched volume at depth in the hangingwall via extensional tectonics while a contracted volume forms via compressional tectonics. The interseismic stress and strain gradients invert at the coseismic stage, with the interseismic dilated volume contracting during the coseismic stage, and vice versa. Moreover, interseismic stress gradients promote coseismic gravitational subsidence of the hangingwall for normal fault earthquakes and elastic uplift for reverse fault earthquakes. Finally, the post-seismic relaxation is characterized by further ground subsidence and uplift for normal and reverse faulting earthquakes, respectively, which is consistent with the faulting style. The fault is the passive feature, with slipping generating the seismic waves, whereas the energy activating the movement is stored mostly in the hangingwall volume. The main source of energy for normal faulting and thrust is provided by the lithostatic load and elastic load, respectively.

We investigated an M_w ∼ 6.2 earthquake doublet on the border of the USA and Canada using ALOS2 Light-of-Sight displacements and GPS measurements. We selected three L-band ALOS-2 interfergorams with temporal baselines of one yr to extract coseismic deformation maps, in which master and slave images were both acquired in July. A subpixel-based alignment and another range spectral splitting techniques under the GAMMA InSAR software framework were applied to improve the interferometric coherence and reduce the effects of phase anomalies in two of the three interferometric pairs due to either ionospheric delay or a potential focusing issues in the generation of the ALOS2 SLC data. The updated interferograms convincingly reveal deformation fringe patterns produced by the two earthquakes. We conducted a nonlinear geophysical inversion to estimate the geometric parameters of the earthquakes with the InSAR and GPS measurements. The best-fitting model shows that a thrust faulting on a reverse fault and left-lateral strike-slip faulting on a nearly vertical fault with the centroid depths of 9.3±0.6 and 8.4±0.7 km, respectively, are most likely responsible for the earthquake doublet. The eastern Denali fault (EDF) and Duke River fault are major active faults in the region and the earthquake doublet could be due to reactivation of the part of the two faults system.

SUMMARY We present ground deformation measurements in the Taupo Volcanic Zone (TVZ) using differential interferomeric synthetic aperture radar (DInSAR) observations collected by ALOS PALSAR during 2006–2010, and compare them with displacement observations from continuous GPS. We acquired and processed DInSAR images from two ascending paths (324 and 325) and one descending path (628) covering the TVZ, and produced linear deformation rates and time series of deformation. The DInSAR results were improved by using a modified version of the small baseline subset (SBAS) algorithm that simultaneously solves for deformation rates and residual topographic noise. The accuracy of the DInSAR displacement rates along line-of-sight to the satellite is 0.5–2 cmyr −1 depending on the number of SAR images and their coherence. We found good agreement between the DInSAR-derived displacement rates and those measured by continuous GPS for the two ascending paths (correlation 0.94 ± 0.01 and 0.89 ± 0.02); the DInSAR uncertainties were too large to make a useful comparison for the descending path (correlation 0.66 ± 0.03). We identified ground deformation due to groundwater and steam extraction for geothermal power. To demonstrate the geophysical application, we modelled the deformation results using simplified sources for some of the geothermal signals using ellipsoidal and tabular approximations.

SUMMARY The MW 7.8 Dusky Sound earthquake of 2009 July 15 was the largest earthquake in New Zealand in the past ∼80 yr and is the only major subduction interface earthquake in the New Zealand historical record. We have estimated the coseismic and early post-seismic slip distribution in the earthquake by inversion of GPS and differential interferometric synthetic aperture radar (DInSAR) observations. We show that slip during the earthquake was highly obliqueandessentiallyintheAustralia–Pacificrelativeplatemotiondirection.Failureoccurred onaca.80by50kmpatchofthesubductioninterfacewithmaximumslip5–6m.Inthisregion, the offshore Alpine Fault carries up to ∼30 mm yr –1 of slip before terminating at Resolution Ridge near the southern end of the 2009 slip patch. The southernmost part of the Alpine Fault trace lies near the up-dip end of the 2009 slip patch and the fault probably exists only within the crust of the over-riding plate in this region, terminating at shallow depth where it meets the subduction interface. There is no evidence for rupture of the Alpine Fault during the 2009 event. However, Coulomb stress changes from the subduction earthquake have brought this section of the Alpine Fault closer to failure. In contrast to many subduction zones undergoing oblique subduction, where the slip in major earthquakes is partitioned into more-or-less pure thrustearthquakesonthesubductioninterfaceandstrike-slipearthquakesinthebackarc,thisis a case where the majority of the subduction interface slip is not partitioned, with only a shallow convergence zone west of the strike-slip Alpine Fault undergoing contraction approximately normal to subduction zone strike. North of the 2009 earthquake region the Alpine Fault lies further east relative to the subduction interface and partitioning between strike-slip on the Alpine Fault and trench-normal thrusting on the subduction interface takes place in a more typical fashion. Our results provide the first clear demonstration of non-partitioned oblique slip between the Australian and Pacific plates offshore of southern New Zealand.

SUMMARY A novel, multidimensional small baseline subset (MSBAS) methodology is presented for integration of multiple interferometric synthetic aperture radar (InSAR) data sets for computation of 2- or 3-D time-series of deformation. The proposed approach allows the combination of all possible air-borne and space-borne SAR data acquired with different acquisition parameters, temporal and spatial sampling and resolution, wave-band and polarization. The produced time-series have improved temporal resolution and can be enhanced by applying either regularization or temporal filtering to remove high-frequency noise. We apply this methodology to map 2003–2010 ground deformation of the Virunga Volcanic Province (VVP), North Kivu, Democratic Republic of Congo. The horizontal and vertical time-series of ground displacement clearly identify lava compaction areas, long-term deformation of Mt Nyamuragira and 2004, 2006 and 2010 pre- and coeruptive deformation. Providing that enough SAR data is available, the method opens new opportunities for detecting ground motion in the VVP and elsewhere.